People who have elevated homocysteine in their blood, an amino acid that is
a known biomarker for cardiovascular disease, may also be at an increased
risk of developing age-related macular degeneration (AMD), the leading cause
of blindness in senior citizens. The study is in the January issue of the
American Journal of Ophthalmology.

In this largest study of the relationship of this amino acid and AMD,
researchers measured the fasting plasma homocystein levels of 934
individuals who were participating in an ancillary study of the Age-Related
Eye Disease Study. Five hundred and forty seven people with AMD and 387
control subjects were tested.

This research was conducted at the Massachusetts Eye and Ear Infirmary and
Devers Eye Institute in Portland, Ore.

"We found that elevated homocysteine in the blood may be another biomarker
for increased risk of AMD," said lead author Johanna M. Seddon, MD, director
of epidemiology at the Massachusetts Eye and Ear Infirmary. Seddon is also
an associate professor of ophthalmology at Harvard Medical School.
"Homocysteine can be reduced by dietary intake of vitamins B6, B12, and
folate, so the relationship between this amino acid and AMD deserves further
study."

Researchers found that median values were higher among people with advanced
stages of AMD compared to people without AMD, controlling for age and other
factors. Levels considered high in the clinical setting (above 12 mmol/l)
were also associated with a higher risk of AMD. Seddon's finding adds to the
growing body of evidence that there may be overlapping disease mechanisms
between AMD and cardiovascular diseases.

Age-related macular degeneration is the leading cause of irreversible visual
impairment and blindness among persons aged 60 and older. With the elderly
population steadily growing, the burden related to this loss of visual
function will increase. Limited treatment options exist and prevention
remains the best approach for addressing this public health concern.

Seddon and colleagues first proposed this potential relationship between
homocysteine and AMD in the mid-1990s and published this hypothesis in a
review article in 1999. She and her team previously established that smoking
and nutrition are modifiable factors associated with the development and
progression of AMD. They are now also searching for the genes involved in
the etiology of this increasing cause of blindness.